How much siding for a 1800 square foot 1.5-storey house

1,800 ft² footprint, 1.5 storeys

22squares to order

1,996 ft² of wall after openings, plus 10% waste for a simple rectangle

Siding to order1 square = 100 ft²	22squares
Net wall area2,348 ft² gross less 15% for doors and windows	1,996ft²
Perimeter assumedmeasure yours — an L-shaped house is 15–30% more for the same footprint	174ft
Waste allowancefew corners, few openings, no gables to cut around	10%
J-channelaround every opening and where siding meets the roof	217linear ft
Outside corner posts	54linear ft

Notes

Measure your own perimeter before ordering. The 174 ft above assumes a tidy rectangle about 1.5 times as long as it is wide. An L-shaped or U-shaped house of the same 1,800 ft² has 15 to 30% more wall — and the error runs in the direction that leaves you short on the last day.
The 15% deduction for openings is an average, not your house. A wall of glass on the south elevation, or a house with very few windows, moves it several points either way. If accuracy matters, measure each opening and subtract properly: siding is ordered by the square and the offcuts are not returnable.
Waste is not padding. Every course has to start and stop at a corner or an opening, and the offcut is usually too short to use elsewhere. A 10% allowance on a simple rectangle is normal; gables are the worst because every course is a different length and the angle cut wastes the end.
Order the trim at the same time. J-channel, corner posts, starter strip, undersill and utility trim are separate items, they are colour-matched to a specific production run, and a later top-up can arrive visibly different. Roughly 217 ft of J-channel and 54 ft of corner post for this house.
Order everything in one lot number. Colour varies between production runs, and on a large elevation the difference is visible in daylight. This is the single most common regret on a siding job and it costs nothing to avoid.
Gables are extra and this figure does not include them. A gable end adds roughly half the width times the rise. On a steep roof over a wide house that is easily another square or two, and it is the part most often left out of a quantity take-off.

22 squares, and the perimeter is the assumption to check

Siding is sold by the square — 100 ft² — and the chain from your floor area to that number runs:

perimeter 174 ft → wall 1,996 ft² after taking off simple rectangle% for openings → 22 squares with waste.

That perimeter assumes a tidy rectangle about one and a half times as long as it is wide. An L-shaped or U-shaped house of the same footprint has 15 to 30% more wall, and the error runs in the direction that leaves you short on the last day. Measure yours.

Waste is not padding

Every course starts and stops at a corner or an opening, and the offcut is usually too short to use elsewhere. Gables are the worst: each course is a different length and the angled cut wastes the end.

Order the trim in the same lot

J-channel, corner posts, starter strip, undersill and utility trim are separate items, colour-matched to a production run. A later top-up can arrive visibly different in daylight, and on a large elevation that is the regret people mention years later.

Roughly 217 ft of J-channel and 54 ft of corner post for a house this shape.

Gables are extra, and this figure does not include them

A gable end adds about half its width times its rise. On a steep roof over a wide house that is easily another square or two — and it is the part left out of most take-offs.

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